1. Field of the Invention
This invention relates to a modular spray cooling system and its method of use to cool components that are used in an electronic circuit which requires control of its operating temperature for effective functioning.
2. Background Art
Today, the quest continues for delivering higher electronic power in smaller packages. One aim of the engineer is to design systems, the temperatures of which can be maintained within acceptable limits when subjected to higher electrical load factors. Additionally, the packaging engineer contends with the problems of efficient use of space.
To use limited space efficiently, circuit card-guides conventionally are provided to support electronic components or printed circuit cards within an enclosure. The support arrangement provides stability and restraint under shock and vibration. Also, the arrangement often provides a heat path from a component to its housing. Typically, such arrangements locate electronic cards so that they lie parallel with each other, often with only a narrow space between adjacent cards. Each card may be electronically connected to a plate or backplane that lies perpendicular to the circuit cards. Because of the proximity of the cards within the enclosure and the electrical power generated, heating and consequent temperature rise often occurs if unchecked.
It is known that one way to remove such heat is to deploy fans which draw air over the heated component so that circulation removes heat primarily by convection. But spatial constraints often inhibit efficiency because air circulation is often insufficient to remove the heat generated. One adverse consequence is that the thermal tolerances of the electronic components may be exceeded.
U.S. Pat. No. 5,880,931 which issued on Mar. 9, 1999 discloses a spray-cooled circuit card cage which seals the enclosure and uses spray plates that release a mist of fine droplets of a coolant fluid. The ""931 disclosure observes that considerable cost is involved in sealing the enclosure and supporting each circuit card adjacent to an associated spray plate. The system requires pressure to be applied from an exogenous source to a fluid entry port. Id., Col. 6, lines 47-48.
Also, illustrative of prior art approaches is an evaporative spray coolant for cooling a heat source, as described in U.S. Pat. No. 5,220,804, which issued on Jun. 22, 1993.
In light of problems that are unsolved by previous approaches, it would be desirable to provide a retrofittable cooling system for enclosures that contain electronic components or conductors. As a result, such a retrofittable cooling system may upgrade the enclosure so that it may contain components that dissipate heat at a higher rate. If so, redesign of the enclosure or housing can be avoided. Additionally, savings in space and weight can be realized and expenditures of time and money can be reduced.
The invention is a self-contained modular spray cooling system for cooling electronic components. The system has a sealed enclosure with an inside wall. Attached to the inside wall is a number of plates that include slots which enable sealed circuit card assemblies containing the electronic component to be detachably accommodated. A spray cooling module is removably mountable in a slot near one or more of the sealed circuit card assemblies within the sealed enclosure.
Additional features include a remotely located plate that can optionally be mounted in a card slot. The plate can optionally support individual spray nozzles and/or valves for recovering condensed fluid. In one embodiment, slotted plates on an inside wall may also contain coolant passages that provide a flow of an evaporative coolant.
The modular spray cooling system includes an evaporative coolant, distributed as fine droplets which are evaporated at least partially upon contact with the electronic components. Some of the coolant evaporates before condensation upon contact with a cooled inside wall of the sealed enclosure or with one of the plates. The condensate collects in a reservoir within the sealed enclosure. Coolant passages lead the condensed evaporative coolant from the reservoir to a pump for reuse within the sealed enclosure.
Thus, the system is basically self-contained. It requires no remotely-located plumbing or propellant. Its design allows for the ready removal and replacement of the electronic components that are cooled therewithin.
The invention also includes a method for cooling electronic components. It comprises the steps of:
providing a modular retrofit to an existing sealed enclosure having an inside wall;
locating a plurality of plates defining slots, the plurality of plates being attached to the inside wall, with the option of at least some of the plurality of plates having coolant passages;
priming the sealed enclosure with an evaporative coolant that may recirculate within the sealed enclosure through the coolant passages; and
delivering power to a spray cooling module that is also detachably mountable within the sealed enclosure. The spray cooling module atomizes the liquid coolant through nozzles so that liquid droplets of the coolant are delivered to the electronic component, are vaporized, remove heat associated with the latent heat of vaporization, and thus cool the components.